Positive Drive Differential

Abstract

A positive drive differential assembly including a differential with an input pinion configured to operably engage with a drive shaft so as to permit the drive shaft to rotate the pinion. A bi-directional overrunning clutch assembly is configured to transmit torque between the pinion and two drive axle segments. A pinion disconnect assembly is provided for controlling transmission of rotation to the pinion and including a rotary coupler. A linear actuator is connected to the rotary coupler and configured to translate the rotary coupler between connected and disconnected positions.

1 . A positive drive differential assembly comprising:
 a differential housing;   an input pinion including a pinion gear and a pinion input shaft attached to the pinion gear, the pinion gear located within the differential housing with a portion of the pinion input shaft extending out of an opening in the differential housing, the pinion input shaft configured to operably engage with a drive shaft so as to permit the drive shaft to rotate the pinion shaft;   a bi-directional overrunning clutch assembly located within the differential housing and configured to engage with at least one drive axle segment, the bi-directional overrunning clutch assembly configured to transmit torque, when engaged, between the pinion gear and the drive axle segments, the bi-directional overrunning clutch assembly including:   a ring gear engaged to the pinion gear;   a clutch housing attached to or formed integral with the ring gear wherein the ring gear is positioned radially outward from an inner surface of the clutch housing, the inner surface having a contoured surface formed on at least a portion of the inner surface;   two roller clutch assemblies located radially inward from the inner surface of the clutch housing, each roller clutch assembly including a roll cage with a plurality of spaced apart slots that extend radially through the roll cage from its outer surface to its inner surface, a roll located in each slot and sized so that it can rotate within the slot, and at least one spring biasing the rolls against movement radially outward relative to the roll cage; and   a roll cage coupler positioned between the two roller clutch assemblies for intermittently coupling the two roll cages to limit relative motion of the roll cages with respect to one another; and   two hubs, each hub located radially inward of one of the roller clutch assemblies, the hubs being axially aligned with one another so as to rotate about a common axis, each hub configured to engage with an end of a corresponding drive axle segment, each hub located radially inward from a plurality of the rolls of the associated roller clutch assembly, each hub having a contoured exterior portion with a plurality of recessed channels formed on the contoured exterior portion of the hub, the recessed channels each extending axially along the contoured exterior portion parallel to a longitudinal axis of the hub, the recessed channels are each sized so that a portion of a roll can seat within the channel, the recessed channels are spaced about the circumference of the contoured exterior portion of the hub;   the at least one spring biasing the rolls in its roller clutch assembly such that each of the rolls is seated in one of the recessed channels when the roll in the roller clutch assembly is not overrunning, the seating of the rolls in the recessed channels providing a connection between the associated roll cage and hub so as to cause the roll cage to initially move with its associated hub.   
     
     
         2 . The positive drive differential assembly of  claim 1 , further comprising a pinion bearing located between a portion of the input pinion and the differential housing for permitting the input pinion to rotate with respect to the differential housing. 
     
     
         3 . The positive drive differential assembly of  claim 1 , wherein pinion shaft includes a splined end located outside of the differential housing which is configured to be engaged to a mating splined connection on an end of the drive shaft. 
     
     
         4 . The positive drive differential assembly of  claim 1 , wherein the ring gear is formed integral with, circumscribes and extends radially outward from an outer periphery of the clutch housing. 
     
     
         5 . The positive drive differential assembly of  claim 1 , wherein at least some of the slots in each roll cage extend axially to one edge of the roll cage so as to provide a lateral opening into the slot from an axial end of the roll cage. 
     
     
         6 . The positive drive differential assembly of  claim 5 , wherein the at least one spring is one spring that biases all the rolls in its roll cage assembly radially inward so as to cause the rolls to engage with the recessed channels in its associated hub. 
     
     
         7 . The positive drive differential assembly of  claim 5 , wherein the inner contoured surface of the clutch housing includes a plurality of peaks and valleys, the number of valleys is at least equal in number to the number of rolls in one of the roller assemblies, wherein when no load is applied to the bidirectional overrunning clutch, each roll is located within one of the valleys with the contoured surface tapering inward toward the roll cage on either side of the rolls. 
     
     
         8 . The positive drive differential assembly of  claim 1 , wherein the number of recessed channels in each hub is a multiple of the number of rolls in its associated roller cutch assembly so that, in a resting position, each of the rolls is seated in one of the recessed channels. 
     
     
         9 . The positive drive differential assembly of  claim 1 , wherein each of the hubs includes an axially outer end with an outer surface that is reduced in diameter with respect to the contoured exterior portion, a portion of the axial outer end of one of the hubs extending through a central opening in a cover of the differential housing and a portion of the axial outer end of the other hub extending through a central opening of a main portion of the differential housing. 
     
     
         10 . The positive drive differential assembly of  claim 9 , wherein an axially inward end of one hub has a reduced diameter portion that fits within a recess in an axially inward end of the other hub. 
     
     
         11 . The positive drive differential assembly of  claim 5 , wherein the roll cage coupler includes a center ring with a plurality of teeth extending radially outward from the ring, the number of teeth is the same as or less than the number of slots, each tooth fits into one of the open ends of one of the slots in each of the roll cages, and wherein each tooth has a circumferential width that is less than a width of the open end of the slot. 
     
     
         12 . The positive drive differential assembly of  claim 1 , wherein the roll cage coupler includes a center ring with a plurality of teeth extending radially outward from the ring, each tooth fits into a receptacle in at least one of the roll cages, and wherein each tooth has a circumferential width that is less than a width of its associated receptacle. 
     
     
         13 . The positive drive differential assembly of  claim 12 , wherein the receptacle is one of the slots in the roll cage. 
     
     
         14 . The positive drive differential assembly of  claim 1 , wherein the roll cage coupler is defined by a plurality of teeth extending axially outward from at least one of the roll cages, each tooth fitting into a receptacle in the other roll cage, and wherein each tooth has a circumferential width that is less than a width of its associated receptacle. 
     
     
         15 . The positive drive differential assembly of  claim 1 , wherein the differential assembly is part of a four wheel drive vehicle, the four wheel drive vehicle having a primary drive axle and a secondary drive axle, wherein the positive drive differential assembly is operably coupled to the secondary drive axle. 
     
     
         16 . The positive drive differential assembly of  claim 15 , wherein there is a second positive drive differential assembly that is operably coupled to the primary drive axle. 
     
     
         17 . The positive drive differential assembly of  claim 1 , wherein a support is provided between each hub and the differential housing. 
     
     
         18 . A differential assembly for a four wheel drive vehicle, the four wheel drive vehicle having a primary drive axle and a secondary drive axle, the secondary drive axle having two drive axle segments, the differential assembly configured to operably couple to the secondary drive axle, the differential assembly comprising:
 a differential housing;   an input pinion including a pinion gear and a pinion input shaft attached to the pinion gear, the pinion gear located within the differential housing with a portion of the pinion input shaft extending out of an opening in the differential housing, the pinion input shaft configured to operably engage with a drive shaft so as to permit the drive shaft to rotate the pinion shaft;   a bi-directional overrunning clutch assembly located within the differential housing and configured to engage with the two drive axle segments, the bi-directional overrunning clutch assembly configured to transmit torque, when engaged, between the pinion gear and the drive axle segments, the bi-directional overrunning clutch assembly including:   a ring gear engaged to the pinion gear;   a clutch housing attached to or formed integral with the ring gear wherein the ring gear is positioned radially outward from an inner surface of the clutch housing, the inner surface having a contoured surface formed on at least a portion of the inner surface;   two roller clutch assemblies located radially inward from the inner surface of the clutch housing, each roller clutch assembly including a roll cage with a plurality of spaced apart slots that extend radially through the roll cage from its outer surface to its inner surface, a roll located in each slot and sized so that it can rotate within the slot, and at least one spring biasing the rolls against movement radially outward relative to the roll cage; and   a roll cage coupler positioned between the two roller clutch assemblies for intermittently coupling the two roll cages to limit relative motion of the roll cages with respect to one another; and   two hubs, each hub located radially inward of one of the roller clutch assemblies, the hubs being axially aligned with one another so as to rotate about a common axis, each hub configured to engage with an end of a corresponding drive axle segment, each hub located radially inward from a plurality of the rolls of the associated roller clutch assembly, each hub having a contoured exterior portion with a plurality of recessed channels formed on the contoured exterior portion of the hub, the recessed channels each extending axially along the contoured exterior portion parallel to a longitudinal axis of the hub, the recessed channels are each sized so that a portion of a roll can seat within the channel, the recessed channels are spaced about the circumference of the contoured exterior portion of the hub;   the at least one spring biasing the rolls in its roller clutch assembly such that each of the rolls is seated in one of the recessed channels when the roll in the roller clutch assembly is not overrunning, the seating of the rolls in the recessed channels providing a connection between the associated roll cage and hub so as to cause the roll cage to initially move with its associated hub.   
     
     
         19 . A four wheel drive vehicle comprising:
 a motor operably coupled to a transmission, the transmission configured to transmit power from the engine to primary and secondary drive shafts;   the primary drive shaft having a first end operably connected to the transmission for receiving rotary motion from the transmission, and a second end connected to a primary differential;   a primary drive axle including two primary drive axle segments, each primary drive axle segment having one end connected to a ground engaging wheel and the opposite end operably connected to the primary differential, the primary differential transmitting rotary motion from the primary drive shaft to the primary drive axle;   the secondary drive shaft having a first end operably connected to the transmission for receiving rotary motion from the transmission, and a second end connected to the pinion input shaft of the positive drive differential assembly of  claim 1 ; and   a secondary drive axle including two secondary drive axle segments, each secondary drive axle segment having one end connected to a ground engaging wheel and the opposite end operably connected to one of the hubs in the positive drive differential assembly, the positive drive differential assembly configured to transmit rotary motion from the secondary drive shaft to the secondary drive axle.   
     
     
         20 . A four wheel drive vehicle comprising:
 a motor operably coupled to a transmission, the transmission configured to transmit power from the engine to primary and secondary drive shafts;   two positive drive differential assemblies according to  claim 1 ;   the primary drive shaft having a first end operably connected to the transmission for receiving rotary motion from the transmission, and a second end connected to the pinion input shaft of one of the positive drive differential assemblies; and   the secondary drive shaft having a first end operably connected to the transmission for receiving rotary motion from the transmission, and a second end connected to the pinion input shaft of the other positive drive differential assembly.